1. Technical Field
The following description relates to one or more development agent supply devices configured to supply charged development agent to an intended device.
2. Related Art
A development agent supply device has been known that includes a development agent holding member (a development roller), an upstream development agent transfer unit, and a downstream development agent transfer unit.
The development agent holding member is disposed to face an electrostatic latent image holding body (a photoconductive drum) in a predetermined development area. The development agent holding member has a development agent holding surface on which charged development agent is held and carried.
The upstream development agent transfer unit has an upstream transfer surface, which is disposed upstream relative to the development area in a moving direction of the development agent holding surface (i.e., in a rotational direction of the development roller) so as to face the development agent holding surface across a predetermined distance. The upstream development agent transfer unit is configured to generate an upstream transfer electric field (i.e., an electric field for transferring the development agent held on the upstream transfer surface from an upstream side to a downstream side in the moving direction of the development agent holding member).
The downstream development agent transfer unit has a downstream transfer surface, which is disposed downstream relative to the development area in the moving direction of the development agent holding surface so as to face the development agent holding surface across a predetermined distance. The upstream development agent transfer unit is configured to generate a downstream transfer electric field (i.e., an electric field for transferring the development agent held on the downstream transfer surface from an upstream side to a downstream side in the moving direction of the development agent holding member).
In the above configuration, the electric fields, for transferring the charged development agent from an upstream side to a downstream side in the moving direction of the development agent holding member, are generated in spaces on the upstream transfer surface and the downstream transfer surface. Thereby, the development agent is transferred, on each of the upstream transfer surface and the downstream transfer surface, from the upstream side to the downstream side in the moving direction of the development agent holding member.
The development agent, carried by the upstream development agent transfer unit, is transferred onto the development agent holding surface in a position where the upstream transfer surface faces the development agent holding surface. Thereby, the development agent adheres to the development agent holding surface. Namely, the development agent is held and carried on the development agent holding surface.
A part of the development agent held on the development agent holding surface is supplied and consumed in the development area to develop an electrostatic latent image. In other words, when reaching the development area, the development agent held on the development agent holding surface partially adheres to positions, corresponding to the electrostatic latent image, on an electrostatic latent image holding surface that is a circumferential surface of the electrostatic latent image holding body.
The remaining part, of the development agent held on the development agent holding surface, which has not adhered to the electrostatic latent image holding surface (i.e., which has not been consumed in the development area), is retrieved by the downstream development agent transfer unit, and then transferred, on the downstream transfer surface, from the upstream side to the downstream side in the moving direction of the development agent holding surface.